1. Field of the Invention
This invention relates to a recording liquid for high-quality high-speed recording with rapid fixing and excellent water resistance on paper specifically designed for ink jet recording and other kinds of paper (e.g., for business and domestic use such as copying paper, writing paper, bond paper, continuous business form paper, etc. and various cloths). The recording liquid of the present invention is excellent in storing stability and is also related to a recording method by use thereof.
2. Related Background Art
Ink jet recording systems recording by forming ink droplets by various ink ejection methods and attach some or all of the ink droplets onto a recording medium such as paper, converted paper, plastic film, fabric, etc. Inks used ink jet recording systems include those having various dyes or pigments dissolved or dispersed in a liquid medium comprising water, or water and a water-soluble organic solvent.
Such ink is generally required to performance as mentioned below in relationship with the recording medium.
(1) To record high quality images without feathering.
(2) To rapidly fix printing ink.
(3) To not clog printer nozzles, even when printing is interrupted.
(4) To provide a good frequency response characteristic which is capable of ejecting ink in conformity with the printing speed of the printer.
(5) To stored stably.
(6) To be safe.
(7) To provide durable printed products which are water and light-resistant etc.
In order to satisfy some or all of the above requirements, aggressive investigations have been made from the standpoint of both ink and device, and considerable progress have been achieved in some required performances.
However, in spite of comprehensive studies up to date, among the above requisite performances, particularly deficient performances at present may include:
(1) no feathering on recording medium having fibers, and excellent fixing characteristic;
(2) excellent frequency response characteristic to be adapted to high speed recording;
(3) excellent water resistance of recorded image even when a water-soluble dye is employed;
(4) excellent storing stability, while satisfying the above performances (1)-(3). These goals have not been sufficiently attained up to now.
First of all, concerning feathering or fixing characteristic on the recording medium having fibers exposed thereon, particularly when printing is effected on ordinary paper such as copying paper, writing paper, bond paper, continuous business form paper, etc., there are problems such that feathering occurs along the fibers of paper, and also that fixing characteristic is not sufficient due to the influence of the sizing agent contained therein.
Accordingly, for the purpose of improving anti-feathering and fixing performance, there have been attempted a method in which recording is performed with using an ink whose pH is made strongly alkaline (Japanese Laid-open Patent Publication No. 57862/1981), a method using an ink having a large amount of a surfactant (Japanese Laid-open Patent Publication No. 29546/1980), a method using an ink which is solid at normal temperature and brought into a liquid state by heating (Japanese Laid-open Patent Publication No. 108271/1983), etc. However, the method of performing recording with an ink which is strongly alkaline is dangerous when the ink is touched, and there is also the drawback that both feathering and fixing are not satisfactory in some papers containing a certain kind of sizing agent. In the method using ink with a large amount of a surfactant, feathering may occur quite frequently depending on quality paper, and troubles can occur since the ink may be retracted from the orifice surface to interrupt ejection, or in contrast, the whole orifice surface may be wetted to interrupt ejection, depending on the conditions of the printer head. Further, in the method using an ink which is solid at normal temperature and brought to a liquid state by heating, improvement to some extent with respect to feathering and fixing of print can be seen. However, in such a method, since a feeding device comprising ink dissolution or a heating device within a printer head is required in the design of the printer, there are involved problems that the printer necessarily be greater in size and higher in cost.
Concerning the second problems of the frequency response improvement for high speed recording, most investigations have been made from a mechanical point such as the head construction, etc., and little inquiry has been made up to now on improvement of ejection response frequency with respect to ink.
Generally speaking, frequency response characteristic is improved with decreased ink viscosity, but stability of ejection will also be lowered in accordance therewith. Therefore, it is difficult to develop an ink which has an improved frequency response characteristic while maintaining the ejection stability. Above all, in the on-demand type ink jet system under driving conditions of 1 KHz or higher, there are problems of both inferior frequency response characteristic and inferior ejection stability, and this tendency is more marked when the driving frequency is raised as high as 2 KHz, 4 KHz and is a particularly serious problem in the ink jet system utilizing a piezoelectric element or heat energy.
As for the third problem of water resistance, a large number of methods have been proposed such as using an ink containing an oily dye or pigment, a method of using a special paper having a water-resistance-imparting agent.
However, these methods will cause the near problems of storing stability and increased cost of recording paper.
The fourth problem of storing stability is substantially solved in an aqueous ink comprising conventional water-soluble dye, water-soluble liquid medium, etc., but under the present situation, no inks satisfying all of the performances sufficiently together with the above performaces (1) to (3) are known.